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<refentry id="sd_journal_open">

<refentryinfo>

<title>sd_journal_open</title>

<productname>systemd</productname>

<authorgroup>

<author>

<contrib>Developer</contrib>

<firstname>Lennart</firstname>

<surname>Poettering</surname>

<email>lennart@poettering.net</email>

</author>

</authorgroup>

</refentryinfo>

<refmeta>

<refentrytitle>sd_journal_open</refentrytitle>

<manvolnum>3</manvolnum>

</refmeta>

<refnamediv>

<refname>sd_journal_open</refname>

<refname>sd_journal_open_directory</refname>

<refname>sd_journal_open_files</refname>

<refname>sd_journal_close</refname>

<refname>sd_journal</refname>

<refname>SD_JOURNAL_LOCAL_ONLY</refname>

<refname>SD_JOURNAL_RUNTIME_ONLY</refname>

<refname>SD_JOURNAL_SYSTEM</refname>

<refname>SD_JOURNAL_CURRENT_USER</refname>

<refpurpose>Open the system journal for reading</refpurpose>

</refnamediv>

<refsynopsisdiv>

<funcsynopsis>

<funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>

<funcprototype>

<funcdef>int <function>sd_journal_open</function></funcdef>

<paramdef>sd_journal** <parameter>ret</parameter></paramdef>

<paramdef>int <parameter>flags</parameter></paramdef>

</funcprototype>

<funcprototype>

<funcdef>int <function>sd_journal_open_directory</function></funcdef>

<paramdef>sd_journal** <parameter>ret</parameter></paramdef>

<paramdef>const char* <parameter>path</parameter></paramdef>

<paramdef>int <parameter>flags</parameter></paramdef>

</funcprototype>

<funcprototype>

<funcdef>int <function>sd_journal_open_files</function></funcdef>

<paramdef>sd_journal** <parameter>ret</parameter></paramdef>

<paramdef>const char** <parameter>paths</parameter></paramdef>

<paramdef>int <parameter>flags</parameter></paramdef>

</funcprototype>

<funcprototype>

<funcdef>void <function>sd_journal_close</function></funcdef>

<paramdef>sd_journal* <parameter>j</parameter></paramdef>

</funcprototype>

</funcsynopsis>

</refsynopsisdiv>

<refsect1>

<title>Description</title>

<para><function>sd_journal_open()</function> opens

the log journal for reading. It will find all journal

files automatically and interleave them automatically

when reading. As first argument it takes a pointer to

a <varname>sd_journal</varname> pointer, which on

success will contain a journal context object. The

second argument is a flags field, which may consist of

the following flags ORed together:

<constant>SD_JOURNAL_LOCAL_ONLY</constant> makes sure

only journal files generated on the local machine will

be opened. <constant>SD_JOURNAL_RUNTIME_ONLY</constant>

makes sure only volatile journal files will be opened,

excluding those which are stored on persistent

storage. <constant>SD_JOURNAL_SYSTEM</constant>

will cause journal files of system services and the

kernel (in opposition to user session processes) to

be opened. <constant>SD_JOURNAL_CURRENT_USER</constant>

will cause journal files of the current user to be

opened. If neither <constant>SD_JOURNAL_SYSTEM</constant>

nor <constant>SD_JOURNAL_CURRENT_USER</constant> are

specified, all journal file types will be opened.</para>

<para><function>sd_journal_open_directory()</function>

is similar to <function>sd_journal_open()</function>

but takes an absolute directory path as argument. All

journal files in this directory will be opened and

interleaved automatically. This call also takes a

flags argument, but it must be passed as 0 as no flags

are currently understood for this call.</para>

<para><function>sd_journal_open_files()</function>

is similar to <function>sd_journal_open()</function>

but takes a <constant>NULL</constant>-terminated list

of file paths to open. All files will be opened and

interleaved automatically. This call also takes a

flags argument, but it must be passed as 0 as no flags

are currently understood for this call. Please note

that in the case of a live journal, this function is only

useful for debugging, because individual journal files

can be rotated at any moment, and the opening of

specific files is inherently racy.</para>

<para><varname>sd_journal</varname> objects cannot be

used in the child after a fork. Functions which take a

journal object as an argument

(<function>sd_journal_next()</function> and others)

will return <constant>-ECHILD</constant> after a fork.

</para>

<para><function>sd_journal_close()</function> will

close the journal context allocated with

<function>sd_journal_open()</function> or

<function>sd_journal_open_directory()</function> and

free its resources.</para>

<para>When opening the journal only journal files

accessible to the calling user will be opened. If

journal files are not accessible to the caller, this

will be silently ignored.</para>

<para>See

<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>

for an example of how to iterate through the journal

after opening it with

<function>sd_journal_open()</function>.</para>

<para>A journal context object returned by

<function>sd_journal_open()</function> references a

specific journal entry as <emphasis>current</emphasis> entry,

similar to a file seek index in a classic file system

file, but without absolute positions. It may be

altered with

<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>

and

<citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry>

and related calls. The current entry position may be

exported in <emphasis>cursor</emphasis> strings, as accessible

via

<citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Cursor

strings may be used to globally identify a specific

journal entry in a stable way and then later to seek

to it (or if the specific entry is not available

locally, to its closest entry in time)

<citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

<para>Notification of journal changes is available via

<function>sd_journal_get_fd()</function> and related

calls.</para>

</refsect1>

<refsect1>

<title>Return Value</title>

<para>The <function>sd_journal_open()</function>,

<function>sd_journal_open_directory()</function>, and

<function>sd_journal_open_files()</function> calls

return 0 on success or a negative errno-style error

code. <function>sd_journal_close()</function> returns

nothing.</para>

</refsect1>

<refsect1>

<title>Notes</title>

<para>The <function>sd_journal_open()</function>,

<function>sd_journal_open_directory()</function> and

<function>sd_journal_close()</function> interfaces are

available as a shared library, which can be compiled and

linked to with the

<constant>libsystemd-journal</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>

file.</para>

</refsect1>

<refsect1>

<title>History</title>

<para><function>sd_journal_open()</function>,

<function>sd_journal_close()</function>,

<constant>SD_JOURNAL_LOCAL_ONLY</constant>,

<constant>SD_JOURNAL_RUNTIME_ONLY</constant>,

<constant>SD_JOURNAL_SYSTEM_ONLY</constant> were added

in systemd-38.</para>

<para><function>sd_journal_open_directory()</function>

was added in systemd-187.</para>

<para><constant>SD_JOURNAL_SYSTEM</constant>,

<constant>SD_JOURNAL_CURRENT_USER</constant>,

and <function>sd_journal_open_files()</function>

were added in systemd-205.

<constant>SD_JOURNAL_SYSTEM_ONLY</constant>

was deprecated.</para>

</refsect1>

<refsect1>

<title>See Also</title>

<para>

<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>

</para>

</refsect1>

</refentry>